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129 lines
4 KiB
C++
129 lines
4 KiB
C++
/* Copyright (c) 2010, 2012 Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#ifndef FILESORT_UTILS_INCLUDED
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#define FILESORT_UTILS_INCLUDED
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#include "my_global.h"
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#include "my_base.h"
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#include "sql_array.h"
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class Sort_param;
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/*
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Calculate cost of merge sort
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@param num_rows Total number of rows.
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@param num_keys_per_buffer Number of keys per buffer.
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@param elem_size Size of each element.
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Calculates cost of merge sort by simulating call to merge_many_buff().
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@retval
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Computed cost of merge sort in disk seeks.
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@note
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Declared here in order to be able to unit test it,
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since library dependencies have not been sorted out yet.
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See also comments get_merge_many_buffs_cost().
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*/
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double get_merge_many_buffs_cost_fast(ha_rows num_rows,
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ha_rows num_keys_per_buffer,
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uint elem_size);
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/**
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A wrapper class around the buffer used by filesort().
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The buffer is a contiguous chunk of memory,
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where the first part is <num_records> pointers to the actual data.
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We wrap the buffer in order to be able to do lazy initialization of the
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pointers: the buffer is often much larger than what we actually need.
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The buffer must be kept available for multiple executions of the
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same sort operation, so we have explicit allocate and free functions,
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rather than doing alloc/free in CTOR/DTOR.
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*/
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class Filesort_buffer
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{
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public:
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Filesort_buffer() :
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m_idx_array(), m_record_length(0), m_start_of_data(NULL)
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{}
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/** Sort me... */
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void sort_buffer(const Sort_param *param, uint count);
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/// Initializes a record pointer.
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uchar *get_record_buffer(uint idx)
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{
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m_idx_array[idx]= m_start_of_data + (idx * m_record_length);
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return m_idx_array[idx];
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}
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/// Initializes all the record pointers.
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void init_record_pointers()
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{
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for (uint ix= 0; ix < m_idx_array.size(); ++ix)
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(void) get_record_buffer(ix);
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}
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/// Returns total size: pointer array + record buffers.
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size_t sort_buffer_size() const
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{
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return m_idx_array.size() * (m_record_length + sizeof(uchar*));
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}
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/// Allocates the buffer, but does *not* initialize pointers.
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uchar **alloc_sort_buffer(uint num_records, uint record_length);
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/// Check <num_records, record_length> for the buffer
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bool check_sort_buffer_properties(uint num_records, uint record_length)
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{
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return (static_cast<uint>(m_idx_array.size()) == num_records &&
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m_record_length == record_length);
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}
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/// Frees the buffer.
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void free_sort_buffer();
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/// Getter, for calling routines which still use the uchar** interface.
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uchar **get_sort_keys() { return m_idx_array.array(); }
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/**
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We need an assignment operator, see filesort().
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This happens to have the same semantics as the one that would be
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generated by the compiler. We still implement it here, to show shallow
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assignment explicitly: we have two objects sharing the same array.
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*/
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Filesort_buffer &operator=(const Filesort_buffer &rhs)
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{
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m_idx_array= rhs.m_idx_array;
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m_record_length= rhs.m_record_length;
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m_start_of_data= rhs.m_start_of_data;
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return *this;
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}
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private:
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typedef Bounds_checked_array<uchar*> Idx_array;
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Idx_array m_idx_array;
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uint m_record_length;
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uchar *m_start_of_data;
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};
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#endif // FILESORT_UTILS_INCLUDED
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